The present invention relates to a cable assembly providing protection from voltage and current surges resulting from lightning strikes. More specifically, the invention relates to a lightning protective burial cable with conductors suitable for connecting a satellite television antenna to a receiver located within a remote building.
A signal received at an outside satellite television antenna is carried to a receiver inside a home, hotel, or other building via a cable often called a direct burial cable because it is underground for most of its length. Such cables are generally round style, including a plurality of conductors arranged around an insulating core and covered with a protective sheath, or flat style, with individually insulated conductors connected in side-by-side relation.
Typically, an antenna system is designed for a nominal operating voltage and current range which is determined in part by the low power levels required by present-day solid-state electronic components. For that reason, satellite antennas are particularly susceptible to lightning strikes. The high voltage or current surge resulting from a direct strike will damage the electronic components of the system, as well as any apparatus electrically connected to the system, such as a television.
Even if the antenna system is not hit directly, it is very susceptible to damage by ground induced lightning (current conducted through the ground). A lightning bolt emits pulsed electromagnetic radiation over a wide frequency spectrum, some of which may be received by the system. Even if a lightning bolt strikes at or near the antenna, the resulting high voltage ground induced currents will be carried through the system wiring and will damage sensitive electronic components at the antenna and in the building. Such components include the television, receiver, modulator, tracking system, and any apparatus connected to the building's electrical wiring.
A satellite antenna is often located at some distance from the building housing the receiver, generally, over one hundred feet away. The AC potential difference between the building and the antenna depends upon the distance between the two, increasing as the distance increases, and tends to increase the susceptibility of the antenna to direct strikes.
Grounding the antenna itself will divert some of the current resulting from a direct strike, but a shunt can still be formed with any connected electronics. Furthermore, a grounding rod at the antenna does not affect the AC potential difference between the building and the antenna, and does not significantly reduce the possibility of damage to the system electronics. Although a grounding wire connected between the antenna and the building eliminates this potential difference, the sensitive electronic components of the system will still be damaged by direct strikes and ground induced strikes.
It is therefore an object of this invention to provide a cable to connect a satellite television antenna to a receiver located within a building.
It is a further object of this invention to provide a cable wherein a grounding wire is combined with a direct burial cable, thus helping protect a system from damage due to voltage and current surges resulting form direct strikes and ground induced lightning strikes.
It is still a further object of this invention to provide a cable which is of simple design, easy to manufacture, and durable in use.